What Makes a Stable & Bright Quantum Light Emitting Diode?
Before we get into what a quantum light emitting diode (QLED) is, we will first look at the definition of a quantum dot and how they play a role in light emitting diodes (LEDs). After the explanations of the above two, this blog will explore what makes a stable and bright quantum light emitting diode.
What Is A Quantum Dot?
Quantum dots (QDs) are extremely small semiconducting crystals that are used for their electrical and optical properties. When an external source, such as UV light, hits the crystals they become stimulated and emit light as a result. Quantum dots can be adjusted in size, which then impacts the color of light they emit. For example, larger particles emit red-coloured light, and smaller particles emit a blue/green color. Atomic composition of the crystal structure also has an influence on the emitted wavelength of light. By manipulating both particle size and composition, QDs can be engineered to emit colours through the entire visible spectrum.
They have been researched thoroughly since the 1980s and now play an important role in many applications, including photovoltaics, lasers, and light emitting diodes.
What Is A Quantum Light Emitting Diode?
When discussing quantum dots, we often mention them alongside organic light-emitting diodes (OLEDs) for comparison. For the last ten years, OLEDs have been predominantly used in flat panel display technologies because of their ability to produce bright, smooth pictures.
Unfortunately, because OLED displays lack a dedicated light source it means that they do not have the same peak brightness capabilities as liquid crystal displays (LCD) and QD displays, and they present problems with stability and brightness. OLED displays have a light output between 540 and 1,000 nits, but a quantum dot display can provide brightness levels up to 2,000 nits. The higher scale of brightness allows for some of the highest quality imaging ever used on commercial TVs.
Quantum light emitting diodes use more power, but they produce a higher quality of brightness and have a longer lifespan than OLEDs.
How Are Stability And Brightness Maintained?
Perovskites are among the preferred structures of QD formulations, particularly given the evident toxicity of cadmium and even indium-based dispersions. However, perovskite QDs are unstable when used in a solid film, which reduces their quality when used in light-emitting diodes (LEDs). A solution is to use perovskites in metal-organic framework (MOF) thin films, and they can subsequently support bright and stable LEDs.
To maintain stability and brightness in QLEDs, the quantum dot layer has an important role. The thickness of the film and the quality of the quantum dot layer will impact the performance of the brightness and light efficiency, and the layer needs to be as thin as possible for optimal performance.
To improve the stability of the quantum dots, a few strategies are available:
- Efficient packaging
- Surface engineering
- Suppressing ion migration
When ions escape from the layer, degradation occurs. To maintain the stability of the QLEDs, suppressing ion migration is crucial. Ion migration can be suppressed by adding a passivation layer to the surface of the QLED, which enables a longer life and higher photoluminescence as well as making it more resistant to corrosion.
Interested in QLED Solutions?
At Avantama, we have been researching and developing the stability of perovskite quantum dots for many years, which has involved analyzing how quantum dot composition is impacted by temperature, oxygen, water and humidity.
If you would like more information about our research or our quantum dots, please don’t hesitate to get in touch with us.